Your quite right Notso,
TO/GA for pitch is attitude hold/Speed hold or a mix of both, bit compicated!
TO/GA for Roll is track hold from where the TO/GA button was pushed.
The pitch mode will ramain until the MCP Alt is reached or till another mode is selected. Roll mode will remain Track hold until another mode is selected.
For info one push engages a calculated thrust for 2500ft/min climb rate 2nd push gives TO/GA thrust ref, climbs like a home sick angel.
Stu.