Once you've verified it's not a basic electrical problem (such as a fuse or faulty brake switch) using Art's notes and diagrams then there are two approaches I'd consider:

a) Try to clean it up to see if it will now work. Detritus (in my case dog hair) can get into the trans shifter housing and possibly collect in the solenoid spring to restrict movement. Peak down if you can to see how clean it looks. Maybe try a vacuum or compressed air to see if you can clear it. Failing that, you'd want to remove it to the bench for testing and cleaning.

b) Disable it, which basically means removing it. They're a major pain to get at and remove, so see if you can figure a way to disable it by wedging/gluing the solenoid back in the retracted position.

I wouldn't be overly concerned about the safety aspect. As much as it's a safety mechanism, you can't simply knock or pull back on the lever to get it out of Park and have the car start to roll if you also released the park brake. You still have to push in the release button on the knob to move the lever and the PNP switch prevents it from being started in gear, plus there's the key lock cable to make sure it's in Park when you remove the key. All the solenoid does is require you to also have the key in the ignition and depress the brake pedal in order to move it out of Park. Any kid goofing around will soon learn you can push in the shift lock override tab to be able to start moving the lever. If this was a manual trans there would be no shift lock solenoid.

If it's no longer functioning you could replace it, but that's a whole lot easier said than done. The shift lock solenoid used only in the '93 240s with AW trans is p/n 9130005 (it's actually #43 in Art's parts schematic when you look it up in a Volvo parts catalog, so go figure as it sure looks like it ought to be #47, which isn't listed in the catalogs). New ones are not available in the Volvo parts chain and you're only going to find used ones in a '93 240 parts car. Not a lot of '93 240 parts cars out there.

The shift lock solenoid in the later 940 AW trans shifters is similar, but not identical, to the '93 240 ones. In one of my 940s it started misbehaving. First time, a cleaning got it going again, but the second time I decided the mechanism was worn so succumbed and removed it. I don't like disabling safety features either, but after doing it to one 940 I won't hesitate to do it in my other 940 at the first sign of trouble.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now