Pro tip if you like to reload for that *perfect* galaxy and also want a custom set of precursors without having to manually select them:

Find the 'precursor_gamestart_generate.txt' file in your 1780597499 workshop folder.
Insert the following within the Menu country event above the "Deselect All" option:

#Custom Precursor Set
option = {
name = precursor.custom

hidden_effect = {
country_event = { id = precursor_selection.1 }
set_country_flag = precursor_select_1
set_country_flag = precursor_select_4
set_country_flag = precursor_select_5
set_country_flag = precursor_select_7
}
}


You'll need to pay attention to which precursors correspond to which number, but this is listed in the "Exit and spawn precursors" section of that file for easy reference. As many flags can be set as you want, but make sure you choose ones that correspond with the DLC/Mods you have.

Next, open your localization(I just did this in the English one) and add this option at the bottom:

precursor.custom: "§GRCustom Precursor Set§"


This can be done for as many sets as you want. Also back it up in a TXT somewhere because it'll get overwritten with each update.