Currently, accepting/rejecting suggestions via Google Docs API is not possible.
To retrieve the style suggestion, you need to access the textRun
of each paragraph element and check if suggestedTextStyleChanges
exists.
Example:

Code:
function myFunction() {
var suggestions = Docs.Documents.get("doc id");
suggestions.body.content.forEach(obj => {
if(obj.paragraph)
obj.paragraph.elements.forEach(element => {
if(element.textRun.suggestedTextStyleChanges){
Logger.log(element.textRun.content);
Logger.log(element.textRun.suggestedTextStyleChanges);
}
});
});
}
Output:

Edit
In your code, you added "textStyleSuggestionState": { "underlineSuggested": true, }
, but Docs.get
method only accepts suggestionsViewMode
as Query Parameter and the values you can input are:
DEFAULT_FOR_CURRENT_ACCESS - The SuggestionsViewMode applied to the
returned document depends on the user's current access level. If the
user only has view access, PREVIEW_WITHOUT_SUGGESTIONS is applied.
Otherwise, SUGGESTIONS_INLINE is applied. This is the default
suggestions view mode.
SUGGESTIONS_INLINE The returned document has suggestions inline.
Suggested changes will be differentiated from base content within the
document.
Requests to retrieve a document using this mode will return a 403
error if the user does not have permission to view suggested changes.
PREVIEW_SUGGESTIONS_ACCEPTED The returned document is a preview with
all suggested changes accepted.
Requests to retrieve a document using this mode will return a 403
error if the user does not have permission to view suggested changes.
PREVIEW_WITHOUT_SUGGESTIONS The returned document is a preview with
all suggested changes rejected if there are any suggestions in the
document.
The correct way to find all the underlineSuggested: true
is by traversing it in the Response body and use SUGGESTIONS_INLINE
as suggestionsViewMode
.
Example:
Document:

This code will print the string that has underline suggestion:
function get_all_suggestion_accepted() {
var suggestions = Docs.Documents.get("11Tx4uvv5yN_TplT4TIUyEWTZ6bUMTGaensYT20EZ4r0");
suggestions.body.content.forEach(obj => {
if(obj.paragraph)
obj.paragraph.elements.forEach(element => {
if(element.textRun.suggestedTextStyleChanges){
var obj = JSON.parse(JSON.stringify(element.textRun.suggestedTextStyleChanges));
if(obj[Object.keys(obj)[0]].textStyleSuggestionState.underlineSuggested){
Logger.log(element.textRun.content);
}
}
});
});
}
Output:

Note: If you want to view all the suggestions, you have to use SUGGESTIONS_INLINE
in the textStyleSuggestionState
query parameter or remove it as SUGGESTIONS_INLINE
is the default view if you have access to the document. Also, when you use PREVIEW_SUGGESTIONS_ACCEPTED
you won't see any suggestions in the object as it returns a preview of the document with all the suggestions accepted.
Further Reading