I am thinking that using the table-layout CSS attribute would solve some of my problems moving from HTML 1.0 to HTML 5.

I cannot find where in the Editor the table-layout would be an option.

From what I can determine table-layout is still valid. And the Validate HTML function doesn't complain when I manually add it.

Am I missing something?

In the 'code' tab along the left hand side, under CSS3 you have 'display'. Open the plus sign and you will find various options, among them 'table', 'table-cell', 'table-group' etc.

I am on HTML Editor 16.1 Build 808.
Under the Code Tab. the CSS3 Display option does not show Table-layout.

You may well use properties that are not included in the code libraries. Since the actual 'table-layout' property can only be auto or fixed, more or less, you can use it in your files. You can even add it to the code library, it should then be added to CSS2.1 where it was first defined.

I think that table layout is more or less out, since there are now new and better options with e.g. flex and CSS grid.