I have several text boxes where I've used a blank space on a line (ie. Return then space bar keys) to make a space between 2 paragraphs. However I've just added a few more text boxes, done the same and found that the spaces have disappeared when I next open the file.

I can't understand why there is a difference in treatment of the spaces within the same file or how to retain those spaces between paragraphs.

Maybe you have seen this?

There are three types of text objects in Inkscape. The first is regular text. The second is flowed text; this is a text object that includes a rectangular frame. The third is linked-flowed text. This is a text object where the text is flowed into a separate arbitrary shape or path object(s). It is discussed at the end of this chapter. When a text object is selected, its type is shown in the Notification Region.

http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Text.html

I'm not entirely clear what you're doing. Are you creating a text box, which has nothing but a space, as a sort of placeholder to create a double line space? If it has nothing but spaces, how can you tell that it's not there when you open the file the next time? Do you mean that other text has moved into the space?

If you're going to use this file outside of Inkscape, anything that you've typed (even spaces) will not show up. The info tylerdurden referenced explains about flowed text.

But I don't think having used flowed text explains why they don't show up the next time you open the file. I think that's because Inkscape doesn't recognize an empty text box. I've actually made a bug report about this a while ago, where a file can be chock full of empty text boxes, which you can't see, but which are adding bulk to the file. In my opinion, it's better to avoid using flowed text entirely, unless you need it for some specfic reason.

But there are other ways to do this. For example, why not just hit Enter twice to add a line space (or 3 times to add 2 spaces, etc.)

In case the 2 paragraphs will have different styles (size, color, stroke, etc), you could use Snapping and Guides to format the text. Here's some info: Snapping info starts here: http://tavmjong.free.fr/INKSCAPE/MANUAL ... pping.html And just a little below that is about Guides.

If it would help, I could show you a tutorial I made, where I used guides and snapping to format the step by step tutorial. (I mean show you the SVG file, so you can see how I did it.)

Eg, I type this, leave a line space

before I finish. The above line space (Enter x 2) had disappeared every time I re-opened the file.

Eg, I type this, leave a line space

before I finish. The above line space (Enter x 2) had disappeared every time I re-opened the file.

Please provide:

Your operating system info
Version of Inkscape (copy from the Menu:Help>About page)
An example file with some text with the issue.

OSX 10.12.6, Inkscape 0.92. File attached has line spaces between 3 paragraphs which disappeared on saving > closing > re-opening.

Looks like inner line height setting is active.

I'd try selecting the flowed text and click the question-mark button to unset the inner line heights.