After looking a bit it turned out there are tools available for that in the lirc distribution and some of them are already included in LibreELEC.
With "irsimsend" (which is available in LE) you can convert a lircd.conf file to a raw file with pulse/space codes. It's a very simple test tool and writes the raw codes always to simsend.out. By default it'll dump all codes (which isn't too useful), but you can tell it to only dump a single button.
eg with your lircd.conf file saved to panasonic.conf you can do
irsimsend -k KEY_POWER panasonic.conf
mv simsend.out power.raw
irsimsend -k KEY_VOLUMEUP panasonic.conf
mv simsend.out volumeup.raw
...
In the lirc source code I found a "pronto2lirc" python script, it's not installed in LE and by default wants Python3, but also works with Python2. I've attached that script (in a zip) and checked that it works on LE.
You need to create a file with the pronto hex codes of each button all in one line and put the button name followed by a colon at the beginning of each line. eg create a file panasonic.pronto:
poweron:0000 0071 0000 0032 0080 003F 0010 0010 0010 0030 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0030 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0030 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0030 0010 0030 0010 0030 0010 0030 0010 0030 0010 0010 0010 0010 0010 0010 0010 0030 0010 0030 0010 0030 0010 0030 0010 0030 0010 0010 0010 0030 0010 0A98
poweroff:0000 0071 0000 0032 0080 003F 0010 0010 0010 0030 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0030 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0030 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0010 0030 0010 0030 0010 0030 0010 0030 0010 0030 0010 0030 0010 0010 0010 0010 0010 0030 0010 0030 0010 0030 0010 0030 0010 0030 0010 0030 0010 0010 0010 0030 0010 0A98
And then run that through pronto2lirc.py
That'll create a lircd.conf file in the current directory and you can then use irsimsend (with -k poweron, -k poweroff) to create raw files.
so long,
Hias