Identify the polygons you want to combine
Copy the geometry of the first one
Paste the geometry to a document or text editor so it looks like this
SRID=4326;MULTIPOLYGON (((-155.3123124353854 19.45547439040195, -155.3096797300312 19.45648780964702, -155.3093021696954 19.45642117316312, -155.309232495921 19.45682012570725, -155.3088793418205 19.45695731326876, -155.3084376624886 19.45692211225389, -155.3072548675565 19.45774351075747, -155.3067493559833 19.45776015241908, -155.3069973874582 19.45627700895497, -155.3073873674545 19.4557004637839, -155.3057193035156 19.45492555996368, -155.3049127929395 19.45420092681852, -155.3047100563242 19.45356047513968, -155.3044369494019 19.45174713321799, -155.3043038136871 19.45146303454845, -155.3050719175799 19.45099396267783, -155.3054763174223 19.45143792019284, -155.3058589761042 19.45262725050284, -155.3061085814408 19.45277717745483, -155.3063455529744 19.45279457623127, -155.3064364613165 19.45237494037833, -155.3066837575778 19.4523615869708, -155.3068971136592 19.45299169399394, -155.3074501941389 19.4525355551642, -155.3075713530919 19.4519726386892, -155.3070158984156 19.45149998848512, -155.3069672367376 19.45110254223928, -155.3073536657515 19.45103638346764, -155.3077393724964 19.45091919907266, -155.3081011790848 19.45139431269598, -155.3087084750404 19.45096810087114, -155.3087572106854 19.45061024226865, -155.3098297020457 19.45036182450738, -155.3100198158475 19.45086974174745, -155.3106318744333 19.45078028738756, -155.3126795744411 19.45480626606842, -155.3123124353854 19.45547439040195)))
Copy the second geometry
SRID=4326;MULTIPOLYGON (((-155.3072346736887 19.45772993017029, -155.3084486223377 19.45693582812351, -155.3089257232107 19.45695744364129, -155.3092359212701 19.45681573999049, -155.3093081696618 19.4564552945545, -155.3096952786739 19.45647971078466, -155.3122799174389 19.45546356584987, -155.3127154032729 19.45562676598558, -155.3134131824247 19.45628554873549, -155.314324600258 19.45673615811147, -155.314486982368 19.45727703891845, -155.3123470173607 19.45855902091367, -155.3112279465167 19.45928500772916, -155.3104001183499 19.46036680008064, -155.3096790413799 19.46079421468841, -155.309509270904 19.46064440184692, -155.3090254673849 19.46025556534049, -155.3087464338763 19.46013679374128, -155.3083141866889 19.45992298533848, -155.3081873608564 19.45977846743777, -155.307872201344 19.45952826763376, -155.3077015457316 19.45914680722103, -155.3076919065185 19.45859888209783, -155.3076291261075 19.45818221768135, -155.3072346736887 19.45772993017029)))
Combine the two geometry's with a comma after the first parentheses so it should be like SRID=4326;MULTIPOLYGON (((First Geometry)),((Second Geometry)))
The parentheses are really important
SRID=4326;MULTIPOLYGON (((-155.3072346736887 19.45772993017029, -155.3084486223377 19.45693582812351, -155.3089257232107 19.45695744364129, -155.3092359212701 19.45681573999049, -155.3093081696618 19.4564552945545, -155.3096952786739 19.45647971078466, -155.3122799174389 19.45546356584987, -155.3127154032729 19.45562676598558, -155.3134131824247 19.45628554873549, -155.314324600258 19.45673615811147, -155.314486982368 19.45727703891845, -155.3123470173607 19.45855902091367, -155.3112279465167 19.45928500772916, -155.3104001183499 19.46036680008064, -155.3096790413799 19.46079421468841, -155.309509270904 19.46064440184692, -155.3090254673849 19.46025556534049, -155.3087464338763 19.46013679374128, -155.3083141866889 19.45992298533848, -155.3081873608564 19.45977846743777, -155.307872201344 19.45952826763376, -155.3077015457316 19.45914680722103, -155.3076919065185 19.45859888209783, -155.3076291261075 19.45818221768135, -155.3072346736887 19.45772993017029)),((-155.3123124353854 19.45547439040195, -155.3096797300312 19.45648780964702, -155.3093021696954 19.45642117316312, -155.309232495921 19.45682012570725, -155.3088793418205 19.45695731326876, -155.3084376624886 19.45692211225389, -155.3072548675565 19.45774351075747, -155.3067493559833 19.45776015241908, -155.3069973874582 19.45627700895497, -155.3073873674545 19.4557004637839, -155.3057193035156 19.45492555996368, -155.3049127929395 19.45420092681852, -155.3047100563242 19.45356047513968, -155.3044369494019 19.45174713321799, -155.3043038136871 19.45146303454845, -155.3050719175799 19.45099396267783, -155.3054763174223 19.45143792019284, -155.3058589761042 19.45262725050284, -155.3061085814408 19.45277717745483, -155.3063455529744 19.45279457623127, -155.3064364613165 19.45237494037833, -155.3066837575778 19.4523615869708, -155.3068971136592 19.45299169399394, -155.3074501941389 19.4525355551642, -155.3075713530919 19.4519726386892, -155.3070158984156 19.45149998848512, -155.3069672367376 19.45110254223928, -155.3073536657515 19.45103638346764, -155.3077393724964 19.45091919907266, -155.3081011790848 19.45139431269598, -155.3087084750404 19.45096810087114, -155.3087572106854 19.45061024226865, -155.3098297020457 19.45036182450738, -155.3100198158475 19.45086974174745, -155.3106318744333 19.45078028738756, -155.3126795744411 19.45480626606842, -155.3123124353854 19.45547439040195)))
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