I have an fw 1884
and when i assign for instance mixer to and aux button
the mixer comes up but when i want to close it it wont
what im trying to say is can i use the same button to te turn on and off an assigned control?
Does that sound right?
You’re using it as a control surface?
I’m not sure which mixer and aux’s you are referring to - The Tascam or n-Tracks?
As its name implies, COMPUTER Control mode is designed to communicate with the host computer, to control your Digital Audio Workstation (DAW) application software. In COMPUTER control mode, all fader and encoder movements and all keypresses are transmitted to the
host computer and interpreted by the host application software (with the exception of certain global keys like control surface mode controls). In addition, the host computer can send information back to the FW-1884 to update fader positions and light LEDs. In COMPUTER Control mode, the FW-1884 can communicate with the host computer in a number of
different protocols (e.g. Native Mode, Mackie Control Emulation Mode, etc.).
The mixer faders and the transport controls in n-Track (play, rec etc.) can be controlled by an hardware MIDI control surface. You can configure what actions are associated with the MIDI events generated by the control surface faders and buttons in the View/Settings/MIDI faders-control dialog box.
The dialog box shows a list of the defined events and the associated actions. To change an event click on its name in the list, change the desired options in the lower part of the window, then click on an empty part of the list window to save the settings.
If you don't know which events are generated by your control surface, you can select the event you want to edit, click on the ‘Learn' button, then move the control on the control surface. The program will detect which event the control sends and update the ‘MIDI event' settings accordingly.
Hope that’s clear enough.
Clear as a bell - and I don’t even have a control surface. 
Thanks for the info once I started using the learn feature most everything works
on the fw1884
it’s nice to learn.