How do I make a Code Section 266 and IRS Regulations 1.266-1 to capitalize, rather than deduct, property taxes using TurboTax online?

Is this for SCH E rental property? Why would you want to capitalize and not amortize? A capitalized asset is depreciated and the depreciation must be recaptured and taxed in the year you dispose of the asset. Whereas an amortized asset is not depreciated, but is instead deducted over a number of years. Did you mean to say amortize? Also, this is for SCH E right?

This is for vacant land. Originally we were going to build a house, but plans changed and we're trying to sell. I want to put the property tax into the cost basis which needs to be declared annually.

You won't deal with that until the tax year you actually sell the property. In the year you do sell, you'll report the sale in the investments section, sub-section for Stocks, Bonds, Mutual Funds, Other and you'll be able to make adjustments to the cost basis by claiming/reporting the property taxes as carrying costs.

You have to make the election annually - <a rel="nofollow" target="_blank" href="https://www.nolo.com/legal-encyclopedia/tax-deductions-vacant-lands.html">https://www.nolo.com/legal-encyclopedia/tax-deductions-vacant-lands.html</a>

TT is software designed for the masses and handles most, but not all situations.
In your case, since this is outside of what a typical TT user is needing to do, you will most likely need to draft the election in a Word document, attach it to your return and paper file the tax return.  You will not be able to efile the tax return.
This will of course mean a longer time frame in receiving any tax refund if applicable.
If you are mailing the return, make sure you send it certified mail return receipt requested.

Is there no way to just make generic statements or a blank form?

Not with the TurboTax program, there isn't.

Though this may not be a perfect solution, I have used it for the past few years to enable me to file electronically despite this being missing from the software.  I have found a closely related form which can
be filled in with the text needed.  To navigate to it, open form 3115.  You will not use that form or need it, but on the top there are 3 quick zoom links to get you a statement which attaches to your return.  They are Elections Smart Worksheets.  They relate to elections to treat small capital expenditures, for example on a rental property, as Expenses.  The first of them is for small amounts totaling under $2500.  The second is for amounts over that.  None of that matters, you won't use those either.  The third one is for 1.263(a)-3(n) "Election to Capitalize Repair and Maintenance Costs"  This is almost perfect for what you want, except you really want: 1.266-1 Election to Capitalize Carrying Costs which doesn't have a form.  No matter.  The only requirement is that you attach a statement to your return claiming your election, it doesn't affect your tax calculation and is normally the last page of a paper filing.  

SO, I open that third form, then use the empty boxes to type in what is required:

ELECTION TO CAPITALIZE CARRYING COSTS
For the tax year 2018, taxpayer hereby elects under Code Section 266
and IRS Regulations 1.266-1 to capitalize, rather than deduct, property
taxes on vacant lots:
XXX County AZ APN #XXX-XX-XXX-XX 3.5ac Lot $234.56
XXX County AZ APN #XXX-XX-XXX-XX 2.5ac Lot $123.45
etc.

There are plenty of lines to enter to get your statement in, and electronically transmitted as part of your return, and I am betting that in an audit you could easily show you attached the required words to your return, they are there, printed in black and white, even though they are not on a separate page.  They both print as part of your paper return and are transmitted electronically.