Disclaimer: If you do this you can mess up your files. An unsubscribe + resubscribe of the mods in question -should- fix it, and also, you should take backups.

First, find the /scripts/library_ui.lua file in the mod directory. Steam usually puts these in some place like C:\steam\steamapps\workshop\content\1489630\2816161899\content\scripts, but your path may vary.

Then find the line starting and copy to the clipboard that entire function block until the appropriate 'end' block, which in this case is
Then rename this mod's library_ui.lua to library_ui.bak or something so the game doesn't complain about conflict anymore. This will make the mods run together, but you won't be able to actually mount any extra missiles.

To fix that, we need to change the same file in the UI Enhancer mod.

Find the same /scripts/library_ui.lua file in the UI enhancer (c:\Steam\steamapps\workshop\content\1489630\2761300794\content\scripts perhaps?), and make a backup. Then find the same function get_ui_vehicle_chassis_attachments. Paste the version from this mod so that it completely replaces the one in the UI Enhancer's version, and save that file. You need to make sure that you copied the whole function and also pasted over the whole function, so that they start with and end with
If you've done it right, you should now be able to have both mods active and it will work - but you can no longer use just the UI mod -without- this one, or the loadout screen will crash. Likewise, if you do this, you can't complain to QuantX that his mod is broken because you've modified the files, and I can't make it automatic because both mods need to change (different parts of) the same file.