I want to install two dimmers on tied neutrals
Most likely, you would be keeping those neutrals together, and also adding the dimmer neutrals to that group so they are all together.  That would be a configuration one would expect:  


neutral from the supply (service panel, consumer unit etc.) 
neutral to lamp 1
neutral to lamp 2
neutral to dimmer 1
neutral to dimmer 2


Generally, neutrals stay together.  But not always.  One place they don't is GFCI outlets.