I am trying to add Bonus Speed to this Class Feature though Modifiers but it doesn't reflect on the character sheet at all. I'm pretty sure I am doing this correctly.

Add Modifier > Modifier Type - Bonus > Modifier Sub-type - Speed (I have also tried to specify Walking Speed) > Fixed Value - 5

Am I doing something wrong or missing something?

EDIT-

I am just consolidating my issues within one post so I don't spam the forum with different issues that I come across in one project.

Late reply is late, BUT, instead of that, try this:

Add Modifier -> Modifier Type - Bonus -> Modifier Sub-type - Set -> Innate Speed (Walking) -> Fixed Value - 35

also, Edit, oops just saw it was closed, my bad OTL

What if it is not a Fixed speed but rather matches the base walking speed? Example, You gain a swim speed equal to your movement speed.