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@Nebula666 Yes, it is working as expected. As said in the description some of the other vanilla blips do disappear but as you collect the collectibles and the blips of this mod are removed I have noticed the vanilla blips to return. Also as said on the description page, I'm currently not planning any expansions.

@HeySlickThatsMe Never noticed blips disappearing beforehand until I started using this mod. I just tried just adding 100 blips without any custom strings or sprites (so it adds 100 yellow circles with the name "Destination") and the problem still persists. Makes me think it is not just the custom string that causes this and there is something else going on. I wouldn't mind fixing this issue but don't want to spend too much time on this anymore. If anyone has a suggestion let me know and I can try it sometime.

@HeySlickThatsMe

I indeed simply set the Name property ScriptHookVDotNet (which seems to use the native function ADD_TEXT_COMPONENT_SUBSTRING_PLAYER_NAME). I tried it the way you suggested, so setting the name like so:
Function.Call(Hash.BEGIN_TEXT_COMMAND_SET_BLIP_NAME, "STRING");
Function.Call(Hash.ADD_TEXT_COMPONENT_SUBSTRING_TEXT_LABEL, "NUM_HIDDEN_PACKAGES_1");
Function.Call(Hash.END_TEXT_COMMAND_SET_BLIP_NAME, blip.Handle);

It does correctly change the name to the values you listed, unfortunately though I don't see a difference in the number of blips rendered.