You don't say how you would like to do this, do you mean have a multipart symbol instantiated underneath the block? Do you mean auto-generate the symbols from the block definition somehow? You can represent a large symbol broken up into separate gates and you can distribute them across hierarchical blocks too.
Depending on what you want to do it may be worth investigating I/O Designer for this kind of fracturing of parts.
If you still believe what you want to achieve cannot be done in the standard product then you should post an Idea on the Ideas Site: https://na5.brightidea.com/ct/s.bix?c=FDA2FA5D-237C-48D7-A66F-5DA754706D6C
Let's say I have a block called <BLOCK1> with 200 ports
On the top level I want to have 3 symbols called <BLOCK1.A>, <BLOCK1.B>, <BLOCK1.C> each with 1/3 of the ports of <BLOCK1>
When I push into <BLOCK1.A>, <BLOCK1.B>, or <BLOCK1.C> it should take me to the same instance of <BLOCK1>
OK, now I understand. This is not a supported flow in DxDesigner currently, it would work the other way, sub-dividing from the 200 pin part but not as you request. This is clearly an enhancement request and should be posted on the Ideas site for peer review.