It seems to me that these tags are about the same thing. The dominant tag is sentence-structure with 243 questions and a tag wiki excerpt:
Questions concerning the types of words and phrases which are grouped and ordered meaningfully to express a statement, question, or another type of sentence
The tag structure has 19 questions and no tag wiki, all of which look like focusing on sentence structure:
- How can I ask "which one is your favorite/do you like more"?
- Are the sentences 这个杯子有一点儿水 and 一点儿水在杯子里 correct?
- Correction of 我在饭店里把晚饭吃了
- Is 靠 structure "A 靠 B do something"?
- 褒贬句 In chinese language
- 好 vs 住 (in resultative complement)
- How do form "You can borrow the book once [it's returned / C returns in]" in Chinese?
- How do form this sentence "I want (object) to (verb/be) that..." in Chinese?
- Is '我还需要多加练习' okay as a dance video caption?
- What does the '头' in '头一次遇到' mean?
- Has anybody heard of 嵌套结构(nested structure)? The dictionary I use lists 中 as it instead of 单一结构
- Give further examples of morphological alternation patterns such as Verb/Noun (处 chu3 / chu4) and Active/Inactive Verb (好 hao4 / hao3)
- What contributes to negative emotion / sentiment in this example?
- When will we use 来 and 到 after a verb?
- Can I use 完 after all verb to say finish doing activities?
- when will we use 没(mei3) and 不(bu4) before verb in sentences?
- MacOS Keyboard with Predictive Completion produces 心情舒暢
- How to say "we want what is best for our kids"?
- When should 了 be after the verb and when should it be at the end of the sentence?
The difference between [sentence-structure] and [structure] doesn't seem meaningful enough to me. Are there other entities with structure that are not sentences, and that aren't more appropriately covered by another tag?
The other tag constructs has 7 questions, and no tag wiki:
- Sentence construction with 除了, 被，一方面
- 了 vs 是...的 as "factuality markers"
- Is this email correct grammatically and structurally?
- Lists and Conjunctions
- What is the term for alluding to a more formless concept by listing its specific members?
- When is a degree required? or: hai6 vs hou2 vs gei
- MSM equivalent of 倒...不... or 半...不... construct?
After further examination, this tag may have its own specific and correct meaning, as in "grammatical constructions":
a group of words that form a constituent of a sentence and are considered as a single unit;
For example ”是～的“，“快～了”, etc. So this tag might be fine, but:
- it's almost unused
- I wonder if it isn't adequately represented by grammar
Edit: proposed [structure] -> [sentence-structure] synonym