Adjective used as an attributive: "high level of focus" uses the adjective "high" as an attributive to modify "level of focus", emphasizing the degree of focus.
Present participle used as object complement: "allowing them to complete tasks" uses the present participle as an object complement, explaining how high focus can increase efficiency and make completing tasks faster and more accurate.
Infinitive used as adverbial of purpose: "to manage their time and energy effectively" uses an infinitive phrase as an adverbial of purpose, describing the purpose of this focus method, which is to effectively manage time and energy.