Designing a Database Application Which User Can Costumizes Tables

I'm working on developing an application in JavaFX platform with SQLite db that will have mixed functionalities and features of both Note application and Accounting. User can log into program and enter data or view database contents. Simply user have forms that can enter data and save theme in database quickly but must there is a main flexibility for this program. Users won't deal with fixed data elements and can make forms for their own needs and have customized elements (table columns). Users can define new data elements in admin panel with new title and type of data.

I'm not looking for a simple code or anything like that now, I want to know how can be it's scenario. I want to have good analyzed of program that next I will work on coding needs.

1. When user can alter tables, some of data can be lost, how can we deal with this problem? My own solution is only that the program shows a simple alert dialog box that notices user from that data will be lost and let the program run. Is any better idea?

2. When user adds some new columns, we can build that with SQL alter statements but that causes they will sort in end of table and don't have a properly view. I have already read that we can make another table from scratch that we can sort columns in new table. But here we don't understand what column should be in what order. User must be able to drag and drop some columns and make their orders. How can save their orders according to user wants and sorts in a TableView.

Thank you. Please excuse me if I can't speak in English properly.