I've created a FX Chain preset with a button to control each effect within, to turn it on/off.
The FX button is mapped to the effect power on/off button if there is one. One of the effect, has a 'bypass' toggle instead of power on/off. Turning on the FX Chain button triggers the bypass mode of that particular effect. In order to make the FX Chain preset buttons to have standard 'power' buttons - I've edited the FX button that is mapped to the effect bypass toggle - by reversing the Start and End percentage (Start = 100%, End = 0%).
If the FX Chain window is opened during saving, there is no issue the next time the project is opened. All on/off setting is correct.
The following caused the reversed button to sometimes forgot it's setting (no problem with normal buttons) :
First, turn on all buttons.
a. Close FX Chain window, save the project, quit X3.
b. Start X3, open the project, open the FX Chain - setting is correct, all buttons are On.
c. Close FX Chain window, save the project, quit X3.
d. Start X3, open the project, open the FX Chain - reversed button is Off (wrong).. while other buttons are On.
If repeated, a - d seems to be repeated.
Hope the description is clear.. anyone free to reproduce this ? I'll file a bug report later.