Change the Column content withot create a new column

So, i have a table that has a column with tables, like in the image below:

I wanted to get only the 15 first rows from the tables from the column "Personalizar.Data". I wass able to do that creating a new column called "Emissão", as showed on the next image:

And so it goes with other treatments. Always creating a new column with what i want to change on the tables and excluding the previous one.

My question is: there's a way to do all the treatments without creating a new column and removing the previous one? Like just changing the "Personalizar.Data" over and over?

Sorry for my bad english! Hope you guy can understand!