Unless they make a specific Multistrada version you might have to do away with the hand guards to use something like that as they attach to the bar end. Unless you have an earlier, pre DVT, Multi then, if I recall, the handguard doesn't connect to the bar end.
Used one on my Triumph ST and found it to be great. Mine was this https://kaoko.com/ Not cheap but worth it. Moved it to my ST4s and needed to cut hole in the end of the grip for the bolt to go through. I think i needed to adjust the RH handlebar switchgear a little too. Tried something similar (but worse) than this and did not like all the bolts sticking out. https://www.amazon.com/BILLFARO-Motorcycles-Motorcycle-Accelerator-Replaceable/dp/B09537VMRS
Have you looked at the Roadlock solution? Doesn't require any modification, simply a bolt on solution. As said above, the throttle locks won't work with the handguards and spacers at the end of the handlebars. I believe the owner of roadlock also stops by on these forums and posts discounts for forum members. Also, I've never seen a throttle lock, but knowing how thieves work around steering locks, I can see the throttle lock being nothing more than an inconvenience and won't stop a theft, let alone delay it. Edit: just seen this is a cruise control thing... I've seen some friends use various solutions, all end up with some form of issue or break. If it were my 1200, I'd instead look for an aftermarket module for cruise control and get it enabled by a dealer.
The bar ends on mine are exposed(2014) so should slip straight on, I’ve been looking at the tuneboy solution, looks great just pricey.
I used to have something like this, super simple, it held the throttle open on the brake lever but as soon as you throttled off it stopped. I can’t remember when I got mine but it was similar. https://www.returnofthecaferacers.com/motorcycle-accessories/gocruise-throttle-lock/
