Condensing 3 F Horns

Hello! I was wondering if it is possible to condense 3 french horns. Obviously when using 4, dorico will automatically pair 1 with 2 and 3 with 4. However for this score, I wish to put them all on one line. Is this possible?

It’s certainly possible. Ensure that you haven’t set up a separate Horn 1+2 custom condensing groups in Layout Options > Players > Condensing, set Notation Options > Condensing to give Dorico the best chance of condensing whatever the material is onto a single stave, then if necessary use Condensing Changes (on the Engrave menu) to override the global Notation Options specifically for the three horns. Really the only hard limit is that a condensed stave can only have a maximum of two voices running at once (one up-stem, one down-stem) so if the three horns are doing three different things rhythmically, you’ll end up with multiple staves.