要不 … 吧 (how about …)

Float the idea gently

• want / will / need要yàonot不bù … (suggestion)吧ba = "how about … / or else … " — a gentle suggestion.
• want / will / need要yàonot不bùwe / us我们wǒ mento walk走zǒu(suggestion)吧ba = "how about we get going?"
• want / will / need要yàonot不bù floats an alternative when you're unsure.

Situation，want / will / need要yàonot不bù + Suggestion + (suggestion)吧ba

• want / will / need要yàonot不bù offers a way out or a new idea, softened by (suggestion)吧ba.

too太tàitired累lèi了le，how about要不yào bùrest休息xiū xia bit一下yí xià吧ba。

• want / will / need要yàonot不bùrest休息xiū xī(used after a verb) give it…一下yī xià(suggestion)吧ba = "how about we take a break?"

Recap

Read the full reference: HSK 5 grammar — Conjunctions.