Is it possible to modify existing time profiles via the Smart Client? Like modify hours on individual days.
Unfortunately no, there is no possibility to modify the time profiles outside doing it manually in the Management Client.
It is on the wish list for future enhancements to the Configuration API to include this.
I see, would be nice to be able to modify. Is it possible to modify the profiles with code within the Management Client?
No, not even in the Management Client can you modify it by code. I will make a note to Product Management team to you are requesting this, maybe it will help in their prioritization..