[Feature Request] Preselect Tool or Tool Number placeholder for user-script GCode

[codefaux]

Hi there! Fantastic plugin, I love it and use it for literally every single print session. I'll just outline the request, then justify it.

Can we get either a "preselect tool before firing Before Preheating GCode" option, or a placeholder variable to replace with the preheat target tool number?

Recently (I've been HEAVILY modding a printer) I added a second extruder and turned it into an IDEX and some other fancy stuff. I found I had a problem, though.

When I preheat my machine (it has a 350mm x 250mm usable print bed, with both an aluminum and glass layer) it takes a while -- eight minutes or so. I also like to preheat the extruder to a low-ish temperature to heat soak everything nicely before I start a job. Previously, I used the "Before Preheating" box for a quick M104 S185 but -- when using IDEX prints, or just printing with the second unit, the printer has no way to know which tool I'm preheating, so it preheats T0 by default. Then, the actual preheat command from the Preheat plugin fires, and T1 turns on -- as expected -- unfortunately leaving T0 idle, but hot. Not great.

I'd like to set Before Preheating GCode to something like "T{tool_num} \n M104 S185" but simply having Preheat select the tool first would be easier for you and just as effective.

Thanks for your time!

[codefaux]

Further input -- STILL being driven absolutely mad by not being able to control which tool preheat gcode runs on, which tool(s) preheat with no file loaded in Octoprint, etc.

Every time I boot my printer, I have to make sure NOT to click Preheat until after I've loaded a file, or it preheats BOTH hotends against my desires. Maybe I'll just ditch the plugin, all it seems to do anymore is piss me off.