Maybe just change M-click from opening Ufopedia to opening TechTreeViewer on SELL screen?
I guess the info you need most on the SELL screen is:
1/ do I need it for any manufacturing later? R-click
2/ do I need it for any research later? new M-click
Opening Ufopedia is useful on other screens, e.g. BUY screen and EQUIP screen...
EDIT: or a combination of both... if there is a corresponding research topic, open TechTreeViewer on M-click; if there isn't, open Ufopedia
EDIT2: done as follows:
Sell/Sack GUI M-click logic update:
1. if there is a corresponding research topic, open TechTreeViewer
2. if not, try to open Ufopedia
By holding CTRL, you can skip step 1 (and thus try to open Ufopedia directly).