[BUG] Toolchange priming when extruder previously retracted

[studiodyne]

Need expertise for the best way to solve this issue, to write a correct fix.

Extruder fw_retracted (S=-10mm) + Toolchange priming (E=10mm) = NO EXTRUSION.(if E=0 it's drama)
Toolchange doesn't unretract 'fw_retracted' extruders before priming...(and any other negative position extruders), but make a 'blind' retractation after priming.
(ideamaker makes G10 before toolchange for example)

Many solutions:

• Unretract before prime + prime + Retract : Mathematicly perfect, perfect for travel/return, but makes 3 extruder moves... Curious behavior...
• Include values for less moves: Perfect too, but the user will see his extruder makes long moves without understanding why. (unretract + prime at once), but not perfect for travelling because the fw_retraction will be included in 'cutting_recover' that only appears when moved back. Must use ' FS_WIPE' , for travelling , with an active G10... This will makes a long extrusion , move back, retract , unretract ...Curious behavior...
• Add an information in cfg.adv that the retracted G10 value will be included in the priming distance ...Or any information about curious behavior when retracted before toolchange
• Delete G10 ? No! Because ideamaker makes a G11 at the perfect position to resume print.. With 'NO_RETURN enabled', the G10+Txx is made, and the G11 appears on the new color start point and not at the old color endpoint.

Any idea appreciate...

Note: I only want to fix ' fw_retract' configuration, because, impossible to know negative position of extruders in all cases. Some slicers use relative pos, other use total value always positive. The only possibilité to fix this for others negative position is an information in cfg.adv to inform the priming distance must be greater than retract_length

Thks