how to correctly handle "pre-upload" build steps that use serial connection with serial monitor active

[PerennialNovice]

I use STM32 with DFU upload and want to automate the upload process a bit more

So I have connected pins to reset and boot0 inputs and the board resets upon reception of a string sequence
To send them I use post-build steps (I know that is not pre-upload... but it's the only way I found out on how to do this so far)
mode ${serial.port}:115200,N,8,1 >nul & set /p x="&" <nul >\\.\${serial.port}

First, I had the commands directly, but that triggered a build error even on success, so the upload was canceled
So I put the commands in a batch file and forced successful return

@echo off
mode %1:115200,N,8,1 >nul & set /p x="&" <nul >\\.\%1
timeout /t 1
exit /b 0

Now, this seems to work fine...
Only problem is: it does not work when serial monitor is active in sloeber.
Even though it gets disconnected for upload, the post-build step happens to early in the chain of commands and the port is not yet released when my batch is run

Is there any way to get sloeber to release the port earlier?
Can I trigger a command in pre-build steps that closes the serial monitor?
Or a completely other way, like I don't know, are there any "pre-upload" hooks I could use in the platform.txt?

would really be nice to have this :)

[jantje]

The timing of resetting the board before upload is still very hard for some boards (for instance leonardo on linux).
Doing the reset as part of the build is never really going to work because the serial monitor conflict.
The only way I see to get this to work is in the upload code.
If I were you I would try to create a "programmer" and use the programmer and not the uploader.
https://arduino.github.io/arduino-cli/1.4/platform-specification/#upload-using-an-external-programmer
Upload and programmer are basically the same except as a end user you have more control over a programmer.

[PerennialNovice]

Ah, didn't know about that

Thanks for the valuable hint!