How to avoid that a styleclass gets added after I edit a sentence?

The Styleclass attribute in the XML source code

The styleclass attribute is used to store references to the styles used by paragraphs, texts, lists, and tables. Please note that this attribute is a part of the XML format used by HelpSmith.

Styles in the XML source code of a topic

In HelpSmith, you can apply a paragraph style (such as Normal, Heading) to the whole paragraph. In this case, in XML code, it will look like:

<para styleclass="Heading 2">
   <text>Topics in This Help Project</text>
</para>

However, it is also possible to apply a paragraph style or text style to a fragment of text within a paragraph. In this case, in XML code, it will look like:

<para>
      <text styleclass="Heading 3">Note:</text>
      <text styleclass="Normal">You can also access the Compile Project dialog by pressing</text>
</para>

Thus, it depends on whether a style is applied to the whole paragraph or to a fragment of text within a paragraph.

Please note that the XML format is used for the source help project only.

When you export your documentation to the output formats (e.g. Web Help, HTML Help, etc.), HelpSmith will uses these data to generate the final documentation in the HTML, PDF, Markdown, and other formats.

Does that means that the text which has styleclass "Text 78", will be different once it gets compiled into a web help?

If you edit formatting attributes of text (e.g. font, size, bold, etc.) through the Write tab, HelpSmith can create and apply auto-created styles (like Text 78, and so on) as explained here.

How to clean styles in a paragraph

As a solution, you can try the following:

1. In the topic editor, select the whole paragraph.
2. In the Styles pane (View tab|Styles), apply a standard style to the selected paragraph.

Usually, it is recommended to use Heading 1..3 for the titles within a topic, and the Normal style for the main text.

Remark: To apply a style to the selected paragraphs or text, you can simply double-click on that style in the Styles pane.

Auto-created styles can be hidden by default

By default, the Styles pane (View|Styles) in HelpSmith can hide auto-created styles.

To show both user-defined and auto-created styles:

1. Click the File tab, then click Options in the bottom.
2. In the HelpSmith Options window, go to the Styles section.
3. In the Styles section, disable the Show user styles only setting option.
   (So the Styles pane will display user-defined and auto-created styles).
4. Click OK.

Now you can check if the "Text 78" style has some different settings. For example, it can have different formatting attributes (e.g. font, size, bold, etc.), Language setting, etc. And probably this is the reason why the topic editor creates this style.