I overwrote my annual return figure for a linked account. I now want to go back to the default setting, which uses historical annual returns by asset class. How do I do this?

You can reset the annual return back to the default. See the image below: src="https://cdn.livehelpnow.net/clients/21145/kb/resetar_127857c8-89f0-4e9b-bd6e-21ff7005765b.png" id="931088dc-c402-469e-a22c-b5deb0cd435a" alt="resetar" width="90%" height="auto" data-image="931088dc-c402-469e-a22c-b5deb0cd435a [...]

Where do I add an HSA investment if I want to add it manually.

You can manually enter an HSA investment in the Taxable & Tax-Advantaged section as seen below: src="https://cdn.livehelpnow.net/clients/21145/kb/hsa1_989e95a8-9fab-4c24-9c9e-ab9b03aa98aa.png" id="1eaba3d5-c634-4c31-ac89-7d64fa843611" alt="hsa1" width="90%" height="auto" data-image="1eaba3d5-c634-4c31-ac89-7d64fa843611 [...]

Why does my pension payout decline every year even though I entered it as a fixed amount?

If the growth rate of the pension is less than the inflation rate, then the inflation-adjusted (today’s dollars) value of the pension will decline over time. The program defaults to showing projections in today's dollars, so if the cash flow has a growth rate less than the inflation rate, the value in today's dollars will indeed decline each year. [...]

I have plenty of salary income left over to pay for an expense I entered in the Goals & Additional Expenses section. I am not yet retired. The expense starts next year. But this expense is being paid for out of my taxable investments and not my salary. Why is that?

You should only enter a goal/additional expense before retirement if the funds to pay for this expense will not come out of regular salary income. All expenses before retirement (Official Retirement Date Of The Plan) are first funded from contributions that would have gone to investments and then from the investments themselves. Note that the "Official Retirement Date Of The Plan" is determined [...]

How do I change the order in which funds are withdrawn from my investment accounts?

If the program needs to use investment income and/or principal it will use money from the Taxable & Tax-Advantaged accounts first, then Non-Qualified accounts, then Qualified Tax-Deferred accounts last. However, within those sections you can control the order of withdrawal by clicking on the re-order icon and then dragging and dropping rows as you see in the screenshot below. [...]