Hello,
How do you have the H90 connected currently? Are you just using inputs/outputs 1 or 1-2 without using any insert routings?
If that is the case, you can use Dual Mode and connect inputs/outputs 3-4 to your amp’s FX loop. You can then use the Routing menu to decide whether each Preset is on Path 1 (before the preamp) or Path 2 (in the FX Loop).
If you place both of the Presets on Path 1, that will effectively be the same as how you are using the H90 already without an FX Loop.
Below are some relevant chapters from the user manual that should be helpful:
https://cdn.eventideaudio.com/manuals/h90/1.12.5/content/setup/pre-post.html
https://cdn.eventideaudio.com/manuals/h90/1.12.5/content/edit-modes/routing.html#dual-routing
Let me know if you have any questions.
