Currently Drop is priority over use in the BP, arguably it should be the other way around. Regardless you shouldn’t have them on the same button anyway as if it is the other way around then you can’t drop secondary.
You can delete/add gameplay tags during runtime (the gunbase does on grip), to remove grip/drop on trigger and replace it with grip/drop on side grip (like it does when held at the handle for the primary grip).
As for the setup, yeah I found a missing check in the BP from when I converted everything to the cleaner gameplay tag checks. I fixed it and fixed a missing return in the DropOrUseSecondary function as well. The template repository is updated with the corrections.