If you're wanting your hotbar to change when you switch to a new pet, you could simply use the following in a macro /hotbar change 3. So for example: Macro 1 is Eos and Macro 2 is Selene

/macroicon "Summon"
/ac "swiftcast" <me>
/wait 1.4
/ac "summon" <me>
/hotbar change 3

/macroicon "Summon ii"
/ac "swiftcast" <me>
/wait 1.4
/ac "summon ii" <me>
/hotbar change 1