I have a couple of printers that have been pretty heavily modified over the last few years.
Since they are so modified in both hardware and the configuration of Marlin firmware, the values for various setting needs to be adjusted beyond. I've done quite a bit of tuning of Accel, Speed, Linear advance, Jerk, etc.
Working on a new plugin would be a learning curve for me, and I'm sure there are some out there which would be able to develop something like this in a fraction of the time it'd take me.
I think a very useful tool for setting up a modified, custom, or DIY printer would be a plugin to adjust certain settings on the fly. Possibly enabled by password to keep the configuration safe.
Similar to some of the basic controls which are already on the Controls and Temp tabs, would it be possible to add a feature to look through the Gcode for retractions (assumes the slicer is set for it), to change the value before being sent to the printer? I've not investigated it, but perhaps this could be done with Marlin's firmware retraction ability?
Other features which could be provided by sending Gcode, if firmware enabled:
Speed (already present on Control tab)
Extrusion Multiplier (already present on Control tab)
Temperature - Hot end (already present on Temprature tab)
Temperature - Bed (already present on Temprature tab)
M205 [B<µs>] [E] [J] [S<units/s>] [T<units/s>] [X] [Y] [Z]`
M204 [P] [R] [S<accel>] [T]
M900 [K] [L] [S<slot>] [T]
M425 [F] [S<linear>] [X] [Y] [Z] [Z]
These are just a few examples, there may be others.
The ability to save (M500)
The plugin could possibly query the current settings (M503) to determine the active values and what is enabled in firmware.
Since some of these are Gcode, it may be possible to add custom control buttons via existing plugins.
Just a thought for those ambitious people out there!
Thanks for Octoprint!
Rich