Strengthening & Weakening Vectors
You can control the AI’s finer focus during a generation by encasing the text you want to emphasize or weaken with { } for strength, and [ ] for weakening.
This works both in the Text Prompt and in the Undesired Content field.
Examples
1girl, black hair, [[[chibi]]], catgirl under a cherry blossom tree
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1girl, black hair, chibi, catgirl under a cherry blossom tree
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1girl, black hair, {{{chibi}}}, catgirl under a cherry blossom tree
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How it works
The weight of AI focus will be multiplied by 1.05 if you enclose the tags or text you want the AI to focus on more with { and }.
The weight of AI focus will be divided by 1.05 if you enclose the tags or text you want the AI to focus on less with [ and ].
Multiple { or [ inside another will multiply the weight each time, so {{ would result in the enclosed part of the prompt being weighted by 1.1025.
Goose Tip: Don't get confused when using Strengthening and Weakening in the Undesired Content field. There, words in between { } will be more avoided more, and words between [ ] will be avoided less!
Numerical Strengthening & Weakening
Instead of writing like {{{{{this}}}}}, you can specify a numeric emphasis weight by using :: in your prompt. Type the desired weight number directly in front of the :: (e.g. 1.5::) and everything to the right of it will be strengthened by this emphasis weight. To end the strengthened section, just place a :: without a number in front of it. For weakening, you can use numbers between 0.0 and 1.0.
An example prompt could be:
1girl, 1.5::rain, night ::, 0.5::coat ::, black shoes
In this example, rain, night will receive an increased emphasis of 1.5, while coat will be deemphasized to 0.5.
Goose Tip: Additionally, :: also serves to close any open brackets, so if you still like using {} and [], but don’t feel like bothering to balance the brackets, you can simply place a :: at the end of your emphasized section to close them (e.g. {{{{{rain ::), no counting necessary!
Note: Numerical Emphasis is only available on V4 or higher models.
Highlight Emphasis
Whether you're using brackets or numerical emphasis, you may notice the colorful highlighting of the prompt box, which quickly lets you see the effects of what you're typing.
If you are not a fan of this highlighting, you can enable or disable the Highlight Emphasis toggle on your Prompt Settings at any time.
Last but not least, if you have the itch to change the colors, you can use the handy color picker to switch up the vibes of the highlights. Simply navigate to the Theme tab in 
User Settings and go wild!
Note
Technically, every { or ] acts as a x1.05 focus multiplier to everything that's to their right,
and every } or [ acts as a ÷1.05 focus divider to everything that's to their right.
By properly enclosing tags, you essentially apply a multiplication to their focus and then cancel it out.
This means you don't need to use those at the very end of the prompt, since there'd be nothing to their right.
Either way, a good practice is to always close out any strengthening or weakening symbols you use with an equal amount of opposing symbols or a ::, but any complex combination will work according to each symbol's values.
{{1girl, {black hair, chibi,}}} {{catgirl [[under]]}} a {{{{{cherry blossom tree
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