Overview
I tried QuickStatements on wikibase.cloud, so here are my notes.
I referred to the following article.
https://qiita.com/higa4/items/10affb47215def42d8e0
Adding Data
Following the article above, I imported a CSV file.

However, the following error occurred.

The cause was that the required properties were not registered on the independently set up wikibase instance.
Property [[Property:P1814|P1814]] not found
It turned out that properties (especially those with the same IDs as wikidata) need to be registered in advance using WikibaseSync or similar tools.
Therefore, I tried registering the following data, which only includes label-related information.
qid,Lja,Len,Dja,Den,qal1545
,タイトル,title,""""説明,desc,1
As a result, new data was successfully registered as shown below.

Updating Data
Next, I attempted to update Q59 registered above with the following command.
qid,Lja,Len,Dja,Den,qal1545
Q59,変更後のタイトル,updated title,""""変更後の説明,updated desc,1
As a result, all values were successfully updated as shown below.

Summary
This was just a brief example, but I tried QuickStatements. I introduced an example of registration via API in the following article, but I felt that CSV-based registration is a user-friendly feature.
I hope this serves as a helpful reference for others.