I’m almost shocked this isn’t implemented yet 
It should be a very simple thing to do as well, similar to how you can mention team members with the @ command which even works here.
Here’s an example of how it would be useful in practice as well as our context.
I’m a relocation specialist, I help foreigners finding a home here in Portugal, renting or buying it, along with some other services.
On these cases I typically serve families, which as a workaround we started creating “Companies” like “Taylor Family” where we add the different family members.
However some times there are key parties that would be useful to have in there, a few examples include:
- Who the landlord is;
- Who referenced them to us;
- Who sold their appliances for warraty purposes;
- Etc
While we COULD add all of these people on the families and/or the deals page, it feels too cumbersome for such a seemingly simple change.
TL;DR: Make it so we can tag other contacts within notes or properties like the @ command, maybe even use a different symbol to not confuse things, so we can create a note with contacts of interest.