I have faced the exact same situation you described for years and hence my post on this forum on February 6, 2024, that started this thread. The only option you have is to combine your holdings in each category into the three available lines of the TurboTax T1135 form and to netfile your T1 return and the T1135 as is. Then download a T1135 from CRA and complete this form properly, adding as many lines as you need. Make sure the total amounts on the TurboTax T1135 you netfiled match the total amounts on your CRA copy. Then mail in the latter to the CRA with a letter explaining that this T1135 amendment was necessary due to shortcomings of the TurboTax sofware. I have never had any follow-ups or inquiries from CRA.
As the responses from the TurboTax moderators to my questions and those of other members did not give me the confidence that this extra lines issue will be fixed anytime, I have finally taken the step to switch to the other tax software, which allows for at least 15 additional lines (and probably many more).
