Disclaimer: I have no knowledge of AOSP roms, or of the application in the OP. That being said...
File transfer behavior is governed by the system property /data/property/persist.sys.usb.config. This is a text file containing a single string. The settings are "mass_storage,adb" or "mtp,adb". Since this is a system file, it is necessary for the phone to be rooted, and then this file can be edited using a root file explorer. Change the text in the file to mtp,adb (without spaces), save the file, and reboot the phone. UMS, or USB Mass Storage is the first one. This is true for Samsung firmware.
after all it wasn't necessary to restore back, i find out that can select mtp from settings->storage->menu->USB Computer connections then i select mtp or camera or mass storage.
So after using this tip, i can now use BOTH (what is the word you use instead of both when you are talking about 3 and not 2 modes? lol , sorry english not my main language) modes UMS from notification menu+app switch , ant still revert to MTP, or PTP using regular phone menus (previously to the advice on this post if i used this same menus even tho it says MASS STORAGE when i selected this it only showed/connected in INSTALL MODE (dont know what that is) .no matter if i selected from pulldown/notification menu or settings menus.
and thank you to the poster and the app creator. (will also hit thanks button by i wanted to write some words )