I have
not tried this yet, but a solution like this for my previous car worked just fine.
The key is to use 2 so-called "add-a-circuit" widgets, such as
Add-a-Circuit With Fuse. However, those are GROSSLY overpriced in my opinion, look for cheaper ones. Make sure it fits the low-profile Subaru type fuse. Also, you should look up the fuse diagram in your manual (2019 = page 482).
Fuse #2 is labeled "CIGAR" and it's not rocket science to figure out where it might go. Pull the fuse out (there's a puller in the engine fuse box) and with a voltmeter note which side is HOT (the ignition must be ON). Note which pin is which.
Find another fuse that the diagram that looks like from name that it might go directly to the battery. My guess would be one of the IGN fuses. With the ignition off, test which side is HOT.
Take the two add-a-circuits and splice them together. Replace the IGN fuse in the top of one of the add-a-circuits and plug it back into the IGN slot. Measure the pins on the other end of the add-a-circuit to see which one is HOT. CLIP the other pin off, and plug the (now single pin) header into the side of the CIGAR slot that goes to the lighter.
You may need to put a fuse back in the CIGAR add-a-circuit end.
IMPORTANT - the CIGAR fuse is 20A, all of the other fuses are 15A or lower. It is STRONGLY SUGGESTED that you replace the 20A fuse that was in the CIGAR slot to one with a lower rating in the add-a-circuit (spares are in the engine compartment box if I'm remembering correctly). Do your homework and pre-prep, make sure you know which side of the add-a-fuse goes where. Measure 2 or 3 times, insert once. Check with an ohmmeter as to what pin on the add-a-circuit goes where draw it out on paper. Anyone with an engineering or technician degree should be able to figure out the correct pins and where they go.
This is just a bare outline of how I would approach this modification. I TAKE NO RESPONSIBILITY if you somehow mess this up. I have
NOT verified this method by looking at any Subaru electrical schematic. If you aren't electrically inclined, have an engineering buddy do it.
If you do succeed, please post the details here and add/subtract any steps to my candidate procedure above.
