In Excel you can insert data in several types (CSV / TXT) directly into the current sheet, to be more precisely, to the current selected cell, and the data will be added in the cells. No extra steps needed, like opening a separate document and copy the data from there.
In LibreOffice I seriously studied how to get this done, but it seems the data will not be added to the currently open sheet. Insert Sheet unfortunately has nothing to do with ‘insert’, as you read it as ‘insert into current sheet’. But it just opens a new sheet!
How do I really add text data (from a txt file / csv file) to the current spreadsheet? The direct way? Without opening the TXT / CSV file in another window, select from begin to end, copy to clipboard, go to target document, select position, paste data.
Those are much to much steps compared to Excel, in which it´s 1 click that does this all (insert from TXT file / insert from CSV file).
NOTE: In Excel the added data from a file, is placed in the cells of the current sheet. Inserting an OLE object in Libreoffice is not the same function: It does not add data into the cells of the sheet, but it adds it as a separate object, which behaves as separate data. So, you can not (easily) calculate that data together with the data of the rest of the sheet.