Of course. You can assign donations to one or other spouse as you please.
In general if both spouses have sufficient tax payable, it doesn't matter which spouse gets donation credit, it's just the same. What usually does make sense is to combine all donations on one spouse or the other, which is what the software us doing.
If you wish to assign credits to one spouse specifically, you will need to prepare each return separately rather than Yse the joint preparation mode.
Regarding donation carryforward, be aware that this is purely a software feature, not recognised by CRA . They don't track unused donations. They only care about what you claim in the current tax year.
If you have more donation credit than you need, don't claim it now, save it for next year.
