Hi Ann and welcome to EYB. If you have all issues of Cooking Light for a set period you would enter the date range you own. You could not go back to the 90s though as we do not go back that far in our Library listings. The earliest issue we have is from 1/1/2008.
If you just own individual issues, not everything in the range, you call up the magazine using the list in Browse in the right column, and go down the list clicking +Bookshelf for those you own. The problem with having the type of check box you suggest is that we would not then be able to present the back issues and future options to any member adding just one of the issues. What I mean is, how would a check box system differentiate between someone adding their first magazine issue and you wanting to add a lot of issues?
For adding cookbooks from the Library to your Bookshelf it is just one click on +Bookshelf for each book you own. I don't understand how that is different to your suggestion of a check box next to each book that you click then press Enter when you have finished making your selections. Isn't your version one click more? If I have misunderstood, please give further info and I will try to help.