Paste text without line breaks and merge blocks of text

Often, text pasted in a text block from somewhere else, includes line breaks. This results in each line being converted into a separate text block. It's impossible to merge these text blocks into a single coherent text block. This way, the text flow is very annoying and cannot be changed (according to page width, for example). Please, add pasting without formatting (shift-paste) to create a single text block and to allow for merging adjacent text blocks into a single one.