Accessing input values that are inside of an RG from outside of the RG can be tricky. There are some plugins that help with it, such as toolbox plugin (a bit more technical) and Orchestra (need to wrap head around how to implement but is more just logic than technical needs)…this will allow you to run workflows from outside of the RG while accessing input values from the RG.

There are other options as well that can be helpful for other features to be added, but require more development work, so I’d say for you, you might want to check out Orchestra first.