It's an interesting use case - I think Michiel is right and this is currently based on groups, so it's worth grouping the parameters in a way that optional parameters can be conveniently disabled.

I think toggle buttons for a single parameter are implemented only in the alarm templates by default (but I seem to recall this just enables/disables the parameter for alarming, the polling is still there).

Not aware of a way to enable/disable a single parameter within the same group - perhaps something in the DIS extension could allow to easily tweak the protocol to achieve this?

Where enabling/disabling is implemented in the protocol (at group level),
you'd have a table in the element similar to this one here below:

this example is from a SL protocol with HTTP polling, but the principle would be the same for SNMP. Here the developer included also a column to tweak the frequency for each polling group.

In the past, where this was not implemented, I was forced to use different protocol versions for the same device type to trim the unnecessary polling over devices where CPU was a precious resource: where the polling of a specific set of parameters was not relevant for specific device, I'd use a different protocol version with a reduced number of parameters.

E.g. same encoder brand, one with SDI inputs, the others with IP inputs, not worth polling the SDI section for the other elements that were all based on IP inputs.

HTH,
A.